1. Field of the Invention
The present invention pertains to pressure fluid control valves comprising generally cylindrical, axially movable closure members which are supported within a modular valve body by a flexible rolling diaphragm type pressure fluid pilot actuator and a coil biasing spring for rapid, low friction movement between control positions.
2. Background
In the art of pressure fluid control circuits, particularly pneumatic control or so-called logic circuits, it is especially desirable to utilize control valves having closure members which are of low mass, and move relatively free of frictional forces acting thereon so that the valve itself is not a variable in certain control functions.
Another important aspect of pneumatic and hydraulic control valves pertains to the provision of a valve wherein the closure member will form a substantially fluid-tight seal in selected positions to control the flow of fluid through the valve. Zero leakage type control valves are difficult and expensive to manufacture and typically so-called spool type control valves require the provision of separate resilient seal members supported on the valve closure member to perform the sealing function when engaged with a valve seat.
The myriad uses of pneumatic and hydraulic valves in various control circuits also contributes to the significance of providing a valve structure which is economical to manufacture in large quantities and is preferably of modular construction so that various specific valve configurations and functional requirements may be met my interchanging a relatively few number of parts in a particular valve assembly to change the operational characteristics of the valve. Although a great number of different valve designs have been developed in the art of fluid control valves of the type used for pneumatic and hydraulic logic circuits, there has been a need to improve the valve structure to meet the desiderata discussed above as well as to overcome certain other problems in the art of pneumatic and hydraulic control valves. The present invention provides several improvements in valves of the type particularly adapted for pneumatic logic and other types of control circuits as will be appreciated by those skilled in the art upon reading the following.